Hair Cortex Comedo: A Series of 34 CasesWalsh, Sarah N MD; Santa Cruz, Daniel J MD; Hurt, Mark A MDAmerican Journal of Dermatopathology: December 2010 - Volume 32 - Issue 8 - pp 749-754 doi: 10.1097/DAD.0b013e3181e15b2e Original Study Abstract Author Information Hair cortex comedo was described originally in an article detailing 2 cases of a comedo-like clinical lesion that was histologically a keratinous plug with cornification similar to the cortex of the hair shaft. We have collected retro- and prospectively a series of 34 cases of hair cortex comedo. In our series, there was a slight female predominance (Male:Female of 1:1.4), and the mean patient age was 28.8 years. All lesions were solitary, distributed mainly on the head and neck or trunk, and were described clinically as a blue subcutaneous papule or nodule with “cyst” as the most common clinical differential diagnosis. Histologic examination showed a solitary, vertically oriented, uniformly sized oval nodule of compact laminated corneocytes sitting in a patulous invagination lined by epithelium similar to the infundibulum, isthmus, or combinations of them; rarely matrical epithelium was identified. Entrapped melanin (30/34 cases), shadow cells (16/34 cases), and calcification (12/34 cases) were identified commonly. Remnants of a surrounding follicle were noted in 15 cases, with infundibular epithelium in 9 of the cases, isthmic epithelium in 3, and matrical or supramatrical epithelium (or both) in 3. There was an associated dense granulomatous infiltrate in the majority of the cases (25/34). Although hair cortex comedo was thought originally to be a variant of dilated pore of Winer, we believe that these distinctive lesions, which are characterized histopathologically by a uniformly sized vertically oriented dermal plug of laminated corneocytes with entrapped melanin and surrounding granulomatous inflammation, are likely derived from matrical or supramatrical cells (or both). From Cutaneous Pathology, WCP Laboratories Inc., St. Louis, MO. Reprints: Sarah N. Walsh, MD, Cutaneous Pathology, WCP Laboratories Inc., 2326 Millpark Dr St. Louis, MO 63043 (e-mail: firstname.lastname@example.org). © 2010 Lippincott Williams & Wilkins, Inc.